1. Field of the Invention
The present invention relates to a method for manufacturing a cylindrical rotatable brush having a plurality of bristles provided around a center of rotation, a rotatable brush, a charging apparatus using the rotatable brush, an image forming apparatus using the rotatable brush, and a cleaning apparatus for a rotatable brush used in an electrophotographic image forming apparatus.
2. Description of the Related Art
In a known electro photographic image forming apparatus, a photosensitive drum is rotated while a charging apparatus is used to apply a uniform electrostatic charge to a surface of the photosensitive drum, and a light beam is used to scan the surface of the photosensitive drum, thereby forming an electrostatic latent image on the photosensitive drum. A developer is applied to the electrostatic latent image upon the photosensitive drum, thus forming a development image upon the photosensitive drum, the development image is transferred from the photosensitive drum to a recording paper and the development image on the recording paper is fixed by heat and pressure.
Here, the charging apparatus may be one wherein the charge is applied by corona discharge, or one wherein the charge is applied by contact with a brush. With the former corona-discharge type of charging apparatus, the charge is applied to the photosensitive drum in a non-contact manner, so it has an advantage in that the charge on the photosensitive drum surface is uniform. However, it also has a drawback in that it generates large amounts of ozone. On the other hand, with the latter brush-contact type of charging apparatus, a brush to which a bias voltage is applied is brought into contact with the surface of the photosensitive drum, thus applying a charge to the photosensitive drum, and this has an advantage in that virtually no ozone is generated.
For example, in JP 2000-187373A (hereinafter referred to as “Patent Document 1”), the bristles of the rotatable brush are crimped so that they are inclined and the photosensitive drum and rotatable brush are rotated in directions opposite each other so that the charge is applied to the photosensitive drum while their outside edges are moving in the same direction in the areas of brush contact.
However, conventional charging brushes include a metal core around which a brush cloth embedded with a plurality of bristles is wrapped directly, or a metal core with a plurality of bristles electrostatically embedded directly into its periphery. However, the bristles of a rotatable brush are preferably fine and their elasticity is low. For this reason, if a rotatable brush is pressed firmly against the photosensitive drum, then the bristles of the rotatable brush are easily crimped so that the bristles of the rotatable brush no longer achieve uniform contact with the surface of the photosensitive drum. But if the rotatable brush only contacts lightly against the photosensitive drum, the bristles of the rotatable brush again do not achieve uniform contact with the surface of the photosensitive drum. Thus, it had been difficult to apply a uniform charge to the surface of a photosensitive drum with a rotatable brush.
Moreover, such problems with rotatable brushes occur not only with brushes used to apply a charge but also discharge brushes used to make contact with and discharge a photosensitive drum or the like, and also cleaning brushes used to make contact with and clean a photosensitive drum or the like.
The present invention has been devised in consideration of these issues, and provides a method for manufacturing a cylindrical rotatable brush, a rotatable brush, a charging apparatus using a rotatable brush, an image forming apparatus using a rotatable brush, and a cleaning apparatus for a rotatable brush by which it is possible to prevent the disturbance of the bristles of the rotatable brush.